Team

An improvement in fuel efficiency and pollutant reduction within internal combustion (IC) engines requires the ability to measure and interpret the physical and chemical processes that characterize the combustion process. A majority of automobiles in production today operate with the spark-ignition (SI) engine, for which the turbulent-chemistry interaction of a developing flame front must be better understood. Nowadays, the direct-injection (DI) concept is becoming popular for SI engines and places further emphasis to understand turbulent-mixing phenomena within IC engines flows. Advanced laser based diagnostic techniques are at the leading edge of combustion research and provide non-intrusive measurement techniques to resolve multi scalar and vector processes within combustion environments. The development and combination of new laser and optical diagnostic techniques are crucial to obtain further knowledge of the leading combustion processes in IC engines.

Method and Theory

Laser and optical diagnostic techniques are developed and combined to measure flow velocity, unburned gas temperature, and combustion species within a single cylinder optical DISI engine. Several applications of particle image velocimetry (PIV) provide valuable flow measurements to characterize the in-cylinder turbulent flow field. High-speed PIV (4.8 kHz repetition rate) measurements provide the evolution of the flow field throughout an entire cycle, while tomographic PIV (3.3 Hz repetition rate) measurements provide important volumetric flow field information during the intake and compression stroke. High-speed PIV is combined with high-speed toluene laser induced fluorescence (LIF) thermometry to simultaneously measure flow velocity and unburned gas temperature during the compression and expansion stroke of the engine. Multiple detection methods for the toluene-LIF thermometry are used with PIV to measure the transport of cold gas near solid surfaces during late compression and early expansion. Stereoscopic PIV, providing 2-dimensional 3-component (2D3C) velocity information, is also combined with OH LIF measurements to study the turbulent-chemistry interaction of the early flame kernel development for different fuels and fuel/air mixtures. Such measurements provide a deeper understanding of the physical and chemical processes that define mixing and combustion in SI engines as well as provide valuable measurements intended for the development of numerical models for combustion and engine simulations.